It’s dandelion season, and as most people with a lawn will be aware, they are remarkably adaptable little blighters.
In the wild, they proudly bear their flowers on long stalks that can be a foot or more tall, amid a lush thicket of leaves. In the lawn, they cunningly avoid the mower by growing as a totally flat rosette, and popping up flowers on almost non-existent stalks.
My question is, is this simply a natural selection thing or are the individual plants actually learning? It certainly seems to be the latter - at the start of the year before I’ve mown the lawn for the first time, the long flower stalks appear, but after I get the mower out, I’d swear that the exact same plants start growing the short stalks.
Is this just confirmation bias (the plants that would grow taller stalks get beheaded so I never notice them), or can dandelions somehow sense that their flowers are getting chopped off and “know” to start producing shorter stalks? And if it’s the latter, do they pass this variation down to their offspring?
It’s individual plants adapting - they’re perennial and will keep growing even if you stop them flowering, so your lawnmower can’t exert absolute selective pressure on them anyway.
It’s probably a mechanism that’s evolved in response to grazing.
At a guess, it’s probably regulated by a break in some hormone feedcback thing - ripening seeds (or associated structures) often produce hormones that tell the plant “this is working! invest energy in these seeds” - the plant’s reaction to the absence of those hormones is to produce more flowers and try again.
The mechanism making them develop shorter each time might be more complex, but I don’t think it’s all that persistent - if you stop mowing, the plants will try growing taller again, with longer flower stalks.
It would be really interesting to know if they still produce shorter flower stalks if only the leaves are trimmed. I may have to experiment with this now to satisfy my curiosity…
Obtaining genetically identical plants for the experiment should be simple, as they will grow from a small piece of taproot, or they can be cloned by picking a flower before it opens and trimming off the petals and stamens, then standing it in a glass of water - dandelion flowers prevented from pollinating will produce viable seeds parthenogenetically.
Dandelions are weeds, and should treated with weed killer to eliminate them. Mowing them down only helps propigate and spread their seeds across your yard.
Yes, it’s stopping them growing that’s the problem. As a side question, any estimates for how long it will be before the entire temperate landmass of the planet is covered in dandelions? They seem incredibly prolific - wildflower meadows around here are basically just a mass of dandelions nowadays, and roadside grass verges are mostly a sea of yellow. In places the air is thick with the seeds drifting around.
the plant may be using its limited time and resources to flower after an injury to reproduce. other deep taproot weeds (burdock) will do similar. some control can be had with cutting the flower off repeatedly after producing seed but before its maturing, though total root removal is better.
It’s a war you cannot possibly win, because the seeds are so mobile - I don’t see any point in getting all worked up about it, or wasting my time trying to eradicate them.
Grass is probably a minority in my lawn (if it can be called a lawn) - and it makes no difference - for every dandelion in my lawn, there are several hundred out on the public green.
I find the best way to get rid of them is to stick a long-bladed screwdriver down beside the root and waggle it around so you can lift out the whole root. It’s easier when the ground is damp.
It’s surprisingly satisfying pulling out the long taproot - it appeals to the same instinct as squeezing a spot I think.
I do this, only using a forked-head Dandelion Puller specifically made for the task (it’s longer than a screwdriver, too) Very satisfying. It gets the root, and so kills the weed (unlike your lawnmower), and it doesn’t blight your lawn (like weed killer can)
While my neighbor’s lawn has a host of dandelions, I find I only get a few every year that need to be spot-treated, because I eliminate them.
I have gone on a full-on assault of the stupid wild violet, though. I don’t even use that namby-pamby violet killer…it can’t kill the stuff. I just spray roundup on it and deal with a small bare patch of lawn for a month or so while it fills back in with grass. Roundup gets the job done.
It really is - my husband and I keep the really good ones as trophies to show off to the rest of the dandelions in the lawn, to make them think about what they’re doing. We both ooh and aah over pulling out a good one.
They’re crazy, those dandelions.
We use weed-killer on areas where we aren’t really growing anything (like the back alley), but what we’ve found most effective is just digging them out by the root like others have said. You have to be careful of disposal, too - the blooms dry out and turn into seeds if you don’t bag them up and throw them away.
So what do you do if you want to encourage dandelions?
What folks are saying about the “no mercy”, though, I can really get behind if we’re talking about thistles. And those are almost impossible to pull up by the roots: The taproot will break off about a quarter inch below where you grab it.
You could just bury them under rocks. That’s what I do.
as for why you do it – my neighbor down the street has so many dandelions that they’ve completely taken over one side of the lawn. When he cuts his grass, that side looks like a green soda-straw plantation.
I know about the “my lawn wouldn’t be green if it weren’t for the weeds” phenomenon, but a lawn of mostly dandelions doesn’t look remotely right.
